Injection level analysis of bulk recombination lifetime in silicon wafers with the ELYMAT technique has become possible through the development of high-stability semiconductor laser diode modules with digitally tunable optical output power. This allows for the identification of the chemical nature of dominant recombination centers such as iron and other dissolved metals, and oxygen precipitates. Metal silicide precipitates in the surface layer are quantitatively related to the surface recombination velocity which can be obtained using two lasers with distinctly different absorption depths in silicon (two-color technique).